<p>A method and apparatus are disclosed which may comprise predicting the gas lifetime for a gas discharge laser light source for a photolithography process, the light source comprising a halogen contaim'ng lasing gas may comprise: utilizing at least one of a plurality of laser operating input and/or output parameters; utilizing a set of at least one parameter of utilization in the photolithography process to determine a gas use model in relation to the respective input or output parameter; predicting the end of gas life based upon the model and a measurement of the respective input or output parameter. The parameter may comprise a pulse utilization pattern. The method and apparatus may comprise performing gas management for a gas discharge laser light source for a photolithography process, the light source comprising a halogen containing lasing gas comprising: utilizing periodic and frequent partial gas refills comprising an inject comprising a mixture of halogen gas and bulk gas in generally the same ration as the premix ratio provided to the laser in a full gas refill, and in an amount less than two percent of the total gas pressure prior to the injection.</p>
